Diabetes patients need to measure the blood sugar level on a regular basis and inject insulin based on the measured blood sugar level to maintain a normal blood sugar level. To maintain this normal blood sugar level, diabetes patients need to measure the blood sugar level on a regular basis, and sample a small amount of blood from their fingertips using a blood test apparatus. A blood sensor is used to detect the blood sugar level from the sampled blood.
A conventional blood sensor will be explained using FIG. 1 to FIG. 3 (see Patent Document 1). Blood sensor 1 shown in FIG. 1 has: substrate 2 of a flat body; substrate hole 2a formed in substrate 2; a plurality of detection electrodes 3 formed in substrate 2; spacer 4 attached in the upper surface of substrate 2; spacer hole 4a that is formed in spacer 4 and that is coupled to substrate hole 2a; cover 5 attached on the upper face of spacer 4; cover hole 5a that is formed in cover 5 and that is coupled to spacer 4; blood storing part 6 formed of substrate hole 2a, spacer hole 4a and cover hole 5a; supply channel 7 with one end coupled to blood storing part 6; air hole 8 provided at the other end of supply channel 7; detecting section 9 formed of detection electrodes 3; and reagent 10 that is mounted on detecting section 9.
Blood storing part 6 of blood sensor 1 is formed with a hole that vertically penetrates blood sensor 1 of the flat body. That is, the inner diameters of substrate hole 2a, spacer hole 4a and cover hole 5a are made the same, and their center points are arranged concentrically.
With reference to FIG. 2 and FIG. 3, the operation of above blood sensor 1 will be explained.
As shown in FIG. 2A, first, blood sensor 1 attached to a blood test apparatus is made to abut on skin 11 of a patient. Next, puncturing needle 12 is launched in the direction of arrow 13. As a result, puncturing needle 12 penetrates blood storing part 6 of blood sensor 1 and punctures skin 11.
As shown in FIG. 2B, blood 15 flows out from punctured skin 11, and blood drop 15a is formed by the surface tension of outflowing blood 15. Following the outflow of blood 15, blood drop 15a becomes bigger until it contacts supply channel 7. When blood drop 15a contacts supply channel 7, blood drop 15a breaks and blood 15 flows into the interior of blood storing part 6 as shown in FIG. 2C. Then, thanks to the capillary action of supply channel 7, blood 15 is led to detecting section 9 at a burst.
In detecting section 9, blood 15 reacts with reagent 10 to produce a current proportional to the blood sugar level. To realize adequate measurement, it is necessary to stabilize the reaction with reagent 10 by making constant the speed (that is, “in the rate-controlled state”) blood 15 flows into supply channel 7. The blood test apparatus measures the blood sugar level by measuring the current proportional to the blood sugar level. Based on this measured level, basic data of the dose of insulin to administer to a patient is acquired, for example.    Patent Document 1: Japanese Patent Application Laid-Open No. 2001-515377